Nitrogen insertion into the LaFe11.58Si1.42 compound with NaZn13-type crystal structure was carried out in a vacuum quartz tube under a high-purity N2 atmosphere. The crystal structure and the magnetocaloric effect of the nitrides were investigated. It is found that nitrogenation pressure is a very important parameter to obtain LaFe11.58Si1.42 nitrides. In the experimental conditions of lower nitrogen pressure, increasing nitrogenation temperature could cause an obvious nitriding effect. The insertion of interstitial nitrogen atoms leads to lattice expansion and the increase of TC. The Arrott plots of samples show that the magnetic phase transition of the samples changes from the first order to the second order. The nitrogen insertion reduces the magnetic entropy change of LaFe11.58Si1.42 compound